vec3 world_pos0 = uMdl * vec4( co, 1.0 );
vec4 vproj0 = uPv * vec4( world_pos0, 1.0 );
vec4 vproj1 = uPvmPrev * vec4( co, 1.0 );
vec3 world_pos0 = uMdl * vec4( co, 1.0 );
vec4 vproj0 = uPv * vec4( world_pos0, 1.0 );
vec4 vproj1 = uPvmPrev * vec4( co, 1.0 );